canvas: simplify |enable_canvas_2d_image_chromium| logic

Simplify logic around |enable_canvas_2d_image_chromium| in runtime_features.cc.

Bug: 839970
Change-Id: I7371c6ce22e7a2c73013b75c8545e5fc91b983c7
Reviewed-on: https://chromium-review.googlesource.com/1057388Reviewed-by: Daniele Castagna <dcastagna@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Miguel Casas <mcasas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#558711}

content/child/runtime_features.cc

@@ -141,15 +141,12 @@ void SetRuntimeFeaturesDefaultsAndUpdateFromArgs(
   }
 
 #if defined(OS_MACOSX)
-  bool enable_canvas_2d_image_chromium = command_line.HasSwitch(
-      switches::kEnableGpuMemoryBufferCompositorResources) &&
+  const bool enable_canvas_2d_image_chromium =
+      command_line.HasSwitch(
+          switches::kEnableGpuMemoryBufferCompositorResources) &&
       !command_line.HasSwitch(switches::kDisable2dCanvasImageChromium) &&
-      !command_line.HasSwitch(switches::kDisableGpu);
-
-  if (enable_canvas_2d_image_chromium) {
-    enable_canvas_2d_image_chromium =
-        base::FeatureList::IsEnabled(features::kCanvas2DImageChromium);
-  }
+      !command_line.HasSwitch(switches::kDisableGpu) &&
+      base::FeatureList::IsEnabled(features::kCanvas2DImageChromium);
 #else
   bool enable_canvas_2d_image_chromium = false;
 #endif